php - 这是一个PHP错误吗？ (关于延伸)

Question

class A extends B {}
class B extends C{}
class C {}

结果

PHP Fatal error: class 'B' not found ...

如果顺序是这样

class A extends B {}
class C {}
class B extends C{}

一切正常

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PS:如果我删除 C 类{}

class A extends B {}
class B extends C{}

php 告诉我找不到类 'B'，为什么？

php 版本 5.3.4

Answer 1

PHP manual明确提到:

Classes must be defined before they are used! If you want the class Named_Cart to extend the class Cart, you will have to define the class Cart first. If you want to create another class called Yellow_named_cart based on the class Named_Cart you have to define Named_Cart first. To make it short: the order in which the classes are defined is important.